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Instruments / Technical Area	Publication Details	Published
I07-Surface & interface diffraction	Ordered and disordered carboxylic acid monolayers on calcite (104) and muscovite (001) surfaces Sander J. T. Brugman , Paolo Accordini , Frank Megens , Jan-Joris Devogelaer , Elias Vlieg The Journal Of Physical Chemistry C 2 DOI: 10.1021/acs.jpcc.2c01157 Diamond Proposal Number(s): [18591] Open Access Show Abstract ▼ Abstract: The adsorption of carboxylic acid molecules at the calcite (104) and the muscovite (001) surface was investigated using surface X-ray diffraction. All four investigated carboxylic acid molecules, hexanoic acid, octanoic acid, lauric acid, and stearic acid, were found to adsorb at the calcite surface. Whereas the shortest two carboxylic acid molecules, hexanoic acid and octanoic acid, showed limited ordering and a flexible, disordered chain, the two longest carboxylic acid molecules form fully ordered monolayers, i.e., these form highly structured self-assembled monolayers. The latter molecules are oriented almost fully upright, with a tilt of up to 10°. The oxygen atoms of the organic molecules are found at similar positions to those of water molecules at the calcite–water interface. This suggests that in both cases, the oxygen atoms compensate for the broken bonds at the calcite surface. Under the same experimental conditions, stearic acid does not adsorb to K+ and Ca2+-functionalized muscovite mica because the neutral molecules do not engage in the ionic bonds typical for the mica interface. These differences in adsorption behavior are characteristic for the differences of the oil–solid interactions in carbonate and sandstone reservoirs.	May 2022
I07-Surface & interface diffraction	The calcite (104) surface - electrolyte structure: A 3D comparison of surface x-ray diffraction and simulations Sander J. T. Brugman , Paolo Raiteri , Paolo Accordini , Frank Megens , Julian D Gale , Elias Vlieg The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.0c04094 Diamond Proposal Number(s): [18591] Open Access Show Abstract ▼ Abstract: Adsorption and incorporation of ions is known to influence the morphology and growth of calcite. Using surface X-ray diffraction, the interfacial structure of calcite in contact with CaCO3, MgCl2, CaCl2 and BaCl2 solutions was determined. All of these conditions yield a comparable interfacial structure, meaning that there is no significant ion adsorption on the terraces under the investigated conditions. This allows for the first time a thorough comparison in all three dimensions with state-of-the-art computer simulations, involving molecular dynamics based on both DFT and two different force field models. Additionally, the simulated structures are used to calculate the corresponding structure factors, which in turn are compared to those obtained from experiment, thereby avoiding the need for fitting or subjective interpretation. In general, there is a good agreement between experiment and the simulations, though there are some small discrepancies in the atomic positions, which lead to an inadequate fit of certain features characteristic of the structure of water at the interface. Of the three simulation methods examined, the DFT results were found to agree best with the experimental structure.	Jul 2020
I07-Surface & interface diffraction	Monovalent - divalent cation competition at the muscovite mica surface: experiment and theory Sander J. T. Brugman , Ben L. Werkhoven , Eleanor R. Townsend , Paolo Accordini , René Van Roij , Elias Vlieg Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2019.10.009 Diamond Proposal Number(s): [20228] Open Access Show Abstract ▼ Abstract: Hypothesis: Ion adsorption on mineral surfaces depends on several factors, such as the mineral surface structure and the valency, size and hydration of the ion. In order to understand competitive adsorption at mineral surfaces, experimental techniques are required that can probe multiple ionic species at the same time. By comparing adsorption of two different cations, it should be possible to derive the factors governing ion adsorption. Divalent cations are expected to bind stronger to the negatively-charged muscovite surface than monovalent cations. Experiments: Here, the competition between the monovalent Cs+ and the divalent Ca2+ cation for adsorption at the muscovite mica basal plane was investigated using surface X-ray diffraction. Using an extended surface complexation model, we simultaneously fit the measured cation coverages and net surface charges reported in literature. Findings: In order to reproduce those complementary data sets, both cation adsorption and anion coadsorption were included in the surface complexation model. Moreover, the intrinsic muscovite surface charge and the maximum of available adsorption sites had to be reduced compared to existing literature values. Competition experiments revealed that the affinity of Cs+ for the muscovite surface is larger than the affinity of Ca2+, showing that hydration forces are more important than electrostatics.	Oct 2019
I07-Surface & interface diffraction	Concentration-dependent adsorption of CsI at the muscovite - electrolyte interface Sander J. T. Brugman , Eleanor R. Townsend , Mireille M. H. Smets , Paolo Accordini , Elias Vlieg Langmuir DOI: 10.1021/acs.langmuir.8b00038 Diamond Proposal Number(s): [15042] Open Access Show Abstract ▼ Abstract: The interfacial structure of muscovite in contact with aqueous CsI solutions was measured using surface X-ray diffraction for several CsI concentrations (2 - 1000 mM). At CsI concentrations up to 200 mM, Cs+ adsorption is likely hindered by H3O+, as both cations compete for the adsorption site above the muscovite hexagonal cavity. Above this concentration, more Cs+ adsorbs than is required to compensate the negatively charged muscovite surface, which means that co-adsorption of an anion takes place. The I− anion does not co-adsorb in an ordered manner. Moreover, the hydration ring and water layers do not change significantly as function of CsI concentration.	Mar 2018

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